Contemporary regenerative dialysis systems enjoy widespread application. In such systems, a sorbent cartridge filters and regenerates dialysate fluid that is pumped between the dialysis equipment and the patient in a closed-loop path. Tap water can be used to prime the system with fluid. Dialysate is generated in an initial purification process using the sorbent cartridge. Typically, six liters of purified dialysate fluid is sufficient for performing a dialysis procedure.
During the dialysis procedure, the purified dialysate is continually pumped into a dialyzer chamber at an input pump. In the dialyzer chamber, the purified dialysate interacts with the patient's blood at a membrane, where urea particles are transferred from the blood into the dialysate. An output pump draws used dialysate from the dialyzer chamber at an output pump. The used dialysate is pumped through the sorbent cartridge, the chemistry of which is configured to filter and remove the urea particles from the dialysate, thereby purifying the dialysate.
Fluid is removed from a patient over a defined time period during the dialysis procedure. The rate at which the fluid is removed is referred to as the ultrafiltration rate. The ultrafiltration rate of a dialysis procedure is prescribed by a physician, and any variation from the prescribed ultrafiltration rate can result in serious adverse consequences to the patient. It is critical that the ultrafiltration rate remain positive during a procedure so that fluids are removed from the patient. At no time during the procedure should the ultrafiltration rate be negative; such “back-filtration” would result in the delivery of fluid to the patient through the dialyzer.
In regenerative dialysis systems, the ultrafiltration rate is a function of the pumping rate of the input pump, pumping purified dialysate into the dialyzer chamber, relative to the pumping rate of the output pump, pumping used dialysate from the dialyzer chamber. By controlling the relative input pump and output pump rates so that the output pump rate exceeds the input pump rate, the differential between the rates guarantees that fluid is removed from the patient.
Management of the ultrafiltration rate is paramount to a successful and safe dialysis procedure for the patient.